Convergence Insufficiency (CI) occurs when a subject's brain fails to coordinate images from both eyes while trying to focus on a nearby object. When a subject reads or looks at a close object, the subject's eyes must both turn inwardly (convergence) to focus. In studies that used standardized definitions of Convergence Insufficiency, investigators have reported a prevalence of 4.2% to 6% in school and clinic settings. Convergence Insufficiency is a common binocular vision disorder that is often associated with a variety of symptoms, including eyestrain, headaches, blurred vision, diplopia (double vision), sleepiness, difficulty concentrating, movement of print while reading, and loss of comprehension after short periods of reading or performing close activities.
Also, CI can cause difficulty with reading. This may make parents or teachers suspect that a child has a learning disability, instead of an eye disorder. In the past, CI disorder has often gone undetected because CI testing is not included in (1) a pediatrician's eye test; (2) school screenings; or (3) basic eye exams. A person can pass the 20/20 eye chart test and still have CI.
Currently, there is no consensus on norms for existing clinical methods for detecting CI or whether these are the only clinical measures required. Multiple subjective and objective decisions, including estimates of distance and time, are required by both the subject and the clinician. Objective measurements rely on examiner expertise and may be difficult for beginners to observe. Subjective measurements require patient cooperation to attain reliable results. In summary, present clinical methods have significant problems regarding accuracy and reproducibility, because they require subjective feedback from the subject, and because of clinician variability.